1. Field of the Invention
This invention relates to a reformer, a CO shift reactor, a CO reducer, a CO oxidizer, a CO methanation reaction vessel, and the like, used in fuel cells and other uses (hereinafter referred to as a reformer, collectively) and, in particular, to the structures of seams of the reformer, wherein tubular members compose an outer vessel of the reformer, various kinds of internal vessels are disposed within the outer vessel, and flow paths for various kinds of fluids, are united, gas-tight, with plate members that are abutted on the tubular members at their internal surfaces, external surfaces, or both the internal and external surfaces.
2. Description of the Related Art
Seams in a conventional reformer are described in the following taking the generator-type reformer (a reformer in a narrow sense) disclosed in Japanese Patent Laid-Open No. 1995-257901 as an example while referring to FIG. 11. FIG. 11 is a longitudinal sectional view of a heat-exchanging-type reformer.
In FIG. 11, the reformer comprises a gas-tight outer vessel composed of a bottomed outer cylindrical casing 1A as a tubular member and two end plates 1B as plate members closing both ends of the outer cylindrical casing 1A, or both the upper and lower open ends thereof. Fluid flow paths are formed by various tubes, as additional tubular members, and plate members and the like as the tube plates (partition walls) to be united with these tubes at their ends and are disposed within the outer vessel.
FIG. 2 illustrates a first fluid feeding pipe that introduces the material fluid, a first fluid, into the outer vessels (1A, 1B). 3 is a first fluid inlet manifold, and 4 is a first fluid flow path through which the first fluid flows after being introduced through the first fluid inlet manifold 3.
Each first fluid flow path 4 is of a double-tubular structure consisting of a bottomed tubular member, an outer tube 5, and an inner tube 6 contained in the outer tube 5 coaxially as a tubular member with both ends open.
7 in the Figure is a flow path for a second fluid, through which the second fluid from a second fluid feeding pipe 7A passes, while exchanging heat with the first fluid via the double tubes (the outer tube 5 and the inner tube 6) composing the first fluid flow path 4 until it is discharged from a second fluid discharge pipe 7B.
The second fluid flow path 7 is separated from the first fluid inlet manifold 3 by a first end plate 8 as a plate member. Similarly, the first fluid inlet manifold 3 is separated from a first fluid outlet manifold 9 by a second end plate 10 as a plate member separate from the one described above.
By the way, 11 is a bellows connecting the second end plate 4 and the inner tube 6. 12 is a reforming medium and 13 is a first fluid discharge pipe.
The operation of the reformer is now described briefly in the following.
The first fluid introduced from the first fluid feeding pipe 2 into the first fluid inlet manifold 3 within the outer cylindrical casing 1A flows into the first fluid exit manifold 9 after passing through a ring-shaped space formed between the outer tube 6 and the inner tube 5, or the first fluid flow path 4, 4, 4. The reforming medium 12 causing the first fluid as the material fluid to react to reformation is filled in a portion of the first fluid flow path 4, 4, 4, and the first fluid is shifted there to a reformed gas by the reforming medium 12.
The reformed gas thus obtained is sent to the first fluid exit manifold 9 through the inner tube 4 and then fed to fuel cells (not shown) via the first fluid discharge pipe 13.
From the second fluid feeding pipe 7A formed near the bottom of the outer cylindrical casing 1A, a high-temperature combustion gas, the second fluid, is sent out and introduced into the second fluid flow path 7. The combustion gas passes through the outer tube 5 while providing heat via the outer tube 5 to the reforming medium 12 contained therein, or heating the reforming medium 12 from outside, and is discharged from the second fluid discharge pipe 7B.
In the reformer, each seam uniting the first end plate 8 with the outer tube 6, or the second end plate 10 with the inner tube 5 (the seam formed via the bellows 11, in this instance) is formed gas-tight with welding so that the first fluid will not mix with the second fluid. Needless to say, the outer cylindrical casing 1A composing the outer vessel and the covering 1B are welded similarly.
In conventional reformers, every seam uniting tubular members including the inner tube 5, the outer tube 6 and the outer cylindrical casing 1A with plate members abutted on these tubular members including the end plates 8 and 10 and the covering 1B is formed with welding for preventing different fluids mixing, while attaining the formation of fluid leakage-free fluid flow paths.
Conventional reformers of a laminar type, for example, are reported on page 79 and page 202 of the proceedings of the third international fuel cell congress held in Nagoya Congress Center between the 30th Nov. and the 3rd Dec., 1999 under the co-sponsorship of the New Energy and Development Organization (NEDO) and the Fuel Cell Development Information Center.
However, it is difficult to apply automatic welding to the sections where tubular members and board members are welded because such sections include many relatively steep curves, as can be seen from the reformer shown in FIG. 11, thus making it unavoidable to rely on expert workers' manual welding, while making an automatic fabrication or a mass production of reformers and a reduction in the manufacturing cost difficult to attain.
Further, seams formed with welding have an additional problem in that the precision of fabrication is impaired due to the occurrence of weld strains at welded sections.